1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a thin film transistor array substrate and a fabricating method thereof.
2. Description of the Related Art
Generally, a liquid crystal displays (LCD) controls light transmittance of liquid crystal. The LCD includes a lower substrate provided with a thin film transistor array and an upper substrate provided with a color filter array that are attached to each other. A spacer for maintaining a cell gap between the two substrates is provided in a cell gap between the substrates. Liquid crystal fills in the rest of the cell gap. By using an electric field across the liquid crystal between a pixel electrode on the upper substrate and a common electrode on the lower substrate, a picture can be displayed.
The thin film transistor array includes thin film transistors provided at crossings of gate lines and data lines. An alignment film is coated on the thin film transistor array for aligning the liquid crystal. The color filter array is comprised of color filters for implementing a color, a black matrix for preventing a light leakage, and an alignment film coated thereon for the sake of an alignment of the liquid crystal.
FIG. 1 is a plan view showing a structure of the related art thin film transistor array, and FIG. 2 is a cross-section view of the thin film transistor array taken along the II-II′ line in FIG. 1. Referring to FIG. 1 and FIG. 2, the thin film transistor array includes a gate line 2 and a data line 4 provided on a lower substrate 1 crossing each other. A gate insulating film 15 is between the gate line 2 and the data line 4. A thin film transistor 6 is provided at the crossing of the gate line 2 and the data line 4. The gate line 2 supplies gate signals and the data line 4 supplies data signals. A pixel electrode 14 is provided at a pixel area defined by the gate line 2 and the data line 4.
The thin film transistor 6 allows the pixel signal of the data line 4 to be charged and maintained on the pixel electrode 14 in response to the gate signal from the gate line 2. The thin film transistor 6 includes a gate electrode 8 connected to the gate line 2, a source electrode 10 connected to the data line 4 and a drain electrode 12 connected to the pixel electrode 14. The gate electrode 8 and source electrode 10 protrude into the pixel area 5.
The thin film transistor 6 further includes an active layer 17 overlapping the gate electrode 8. A gate insulating film 15 is between the active layer 17 and the gate electrode 8. The active layer 17 provides a channel between the source electrode 10 and the drain electrode 12. The active layer 17 also overlaps the data line 4. An ohmic contact layer 19 for making an ohmic contact with the source electrode 10 and the drain electrode 12 is further provided on the active layer 17.
The pixel electrode 14 is provided at the pixel area 5 and is in contact with the drain electrode 12 of the thin film transistor 6 via a contact hole going through a protective film 21. Thus, an electric field is formed between the pixel electrode 14 to which a pixel signal is supplied via the thin film transistor 6 and the common electrode (not shown) supplied with a reference voltage. Liquid crystal molecules between the lower substrate provided with the thin film transistor array and the upper substrate provided with the color filter array are rotated due to a dielectric anisotropy. Transmittance of a light transmitting the pixel area 5 is differentiated depending upon the rotation extent of the liquid crystal molecules, thereby implementing a gray level scale. The above-mentioned related art thin film transistor array has a problem in that, since the thin film transistor 6 is formed in such a manner to be within the pixel area 5, an effective pixel area for transmitting a light of the pixel area is reduced, which causes a reduction in an aperture ratio.